Making soap

I've wanted to try this ever since I saw Fight Club! I've seen several methods for making soap, but I'm always attracted to using dangerous chemicals, so lye seemed the obvious way to go.

Lye, sodium hydroxide, is an incredibly caustic chemical with a bad boy reputation for removing fingerprints and dissolving corpses. During the second world war, Leonarda Cianciulli liquidised three victims in Italy using the stuff, and Santiago Meza López, "The Stewmaker", claims to have disposed of 300 bodies with it.

I decided to make a floral lavender soap and a macho coffee soap inspired by The Art of Manliness. They say that coffee soap is very good for cleaning harsh smells from your hands.

I used The Sage to get the right quantities of oil, water and lye, and off I went!

Ingredients

Lavender soap

1 litre (916g) of olive oil

286ml cold water

115g lye crystals

20g ground lavender

20g lavender flowers

10ml lavender essential oil

Food colouring (optional)

Coffee soap

1 litre (916g) of olive oil

136ml cold water

115g lye crystals

3 double espressos (totalling 150ml)

1/2 cup of coffee grounds

You'll also need:

Eye protection, a face mask and gloves - I can't overstate how dangerous lye is

1 litre of vinegar - in case you spill lye on yourself you'll need to neutralise it really quickly

Thermometer

Bowls and stirring tools that aren't aluminium or wood - lye will eat through these

A stick blender - it reduces the stirring time from an hour to 5-10 minutes

Moulds to pour the soap into - I used four old takeaway containers with lids

Towels to wrap the moulds

The pictures are all from the lavender soap, but it's the same process for making the coffee version.

Method

First you'll need to make the lye solution. Put on all your protective gear. Mixing lye with water is extremely exothermic, and so it's really important to add the lye crystals to the water and not the other way around! If you're making the coffee version, wait for the espressos too cool, then mix with the water. Make sure you've got 286ml of liquid in total.

Do this outside as the fumes are really nasty, and add the crystals bit by bit, stirring continually. By the time I'd added all the lye, the water had jumped from 10°C to 95°C. You really don't want it to boil.

Now you need that to cool down to 50°C maximum, so leave it outside and heat the oil to about 50°C as well. Once the lye has cooled, pour it gently into the oil and gently mix together. Add the ground lavender and the lavender oil, plus the colour if you're using it, then blend with the stick blender for 5-10 minutes until it's the consistency of thick custard.

Pour some of the lavender flowers into the bottom of the moulds, then add the gloopy soap, seal the moulds and wrap in towels to keep the heat in. Leave for 24 hours for the soap to set.

The next day, pop the soap out of the moulds, cut them up and leave to cure for 6-8 weeks. This allows all the lye to react with all the oil to make soap, called saponification.